Seal assembly

ABSTRACT

A seal assembly seals a first portion of a machine part relative to a second portion of the machine part. The seal assembly includes at least one seal element that contacts the machine part or contacts a component connected with the machine part or that extends with a gap relative to the machine part or to the component connected with the machine part. At least one of the seal element, the machine part and the component connected with the machine part is provided or coated with a material, which has super hydrophobic properties, in the area of the seal element.

The invention relates to a seal assembly that seals a first portion of amachine part relative to a second portion of a machine part, wherein theseal assembly includes at least one seal element that contacts themachine part or contacts a component connected with the machine part orthat extends with a gap relative to the machine part or to the componentconnected with the machine part.

Seal assemblies of this type are well known. They are used as frictional(e.g., radial shaft seal rings) as well as non-frictional seals(labyrinth seals), by means of which a sealing of an area of a componentcan be ensured.

Notwithstanding appropriate usage, it can not always be prevented thatmoisture and dirt enter into the area to be sealed. A corrosion dangerand/or a contamination of the lubricant (oil or grease) results due tosuch an ingress of water, which can lead to operational disruptionsand/or even operational breakdowns. Generally speaking, an improvedprotection against the ingress of moisture can be achieved only byimplementing constructive modifications to the seal assembly, e.g., bydisposing a greater number of seal elements and/or seal lips.

Therefore, the object underlying the invention is to further develop asealing assembly of the above-mentioned type so that an improvedprotection against the penetration of moisture, in particular water, isprovided without having to modify the seal design.

The solution of this object by the invention is characterized in thatthe seal element and/or the machine part and/or the component connectedwith the machine part is provided or coated with a material, which hassuper hydrophobic properties, in the area of the seal element.

The super hydrophobic material preferably has a water contact angle (θ)of at least 150° (for this, see the following embodiments).

The super hydrophobic material includes nano-filaments in anadvantageous manner. In particular, the super hydrophobic material caninclude silicone nano-filaments. Polymethylsilsesquioxane nano-filamentshave proven themselves as a preferred material.

According to one embodiment, the seal assembly can comprise at least oneseal lip, wherein a portion of at least one seal lip is provided orcoated with the material. In particular, it can involve a radial shaftseal. The at least one seal lip can axially or radially contact itscounterface. The seal lip can contact a contact disk that is connectedwith the machine part.

According to an alternative embodiment, however, the seal assembly canalso comprise a labyrinth seal that includes at least one portionforming a gap, wherein the portion forming the gap is provided orcoated, at least partially, with the material. The dimensioning of thegap height is effected in dependence upon the water contact angle of thematerial so that the water drop will be larger than the gap height, inorder to reliably prevent the ingress of water in this case.

The machine part interacting with the seal lip or with the labyrinthseal or the component connected with the machine part can be a shaft ora contact ring that can be provided or coated with the material on itssurface at least in the area of the seal assembly.

The proposed concept is suitable for seals, which operate withcontacting seal elements, as well as for those, which seal in acontact-free manner.

The long-lasting super-hydrophobic effect provides for the formation ofspherical-shaped water drops on planar surfaces using the surfacetension of the water, which drops can roll off (bead off) in aresidue-free manner when inclined. For curved surfaces, such as e.g., inthe case of shafts, the water can form ring-shaped structures(torus-shaped structures) when present in sufficient amounts. Thesealing effect can be bolstered by an advantageous geometry, so that theto-be-excluded water drops are conveyed in the desired direction.

It is advantageous that the water-repelling property is maintained onthe seal and the counterface independent of the surface wear of thecontact surfaces, i.e. it is wear-independent.

Exemplary embodiments of the invention are shown in the drawings.

FIG. 1 shows the radial cross-section through a seal assembly in theform of a radial shaft seal,

FIG. 2 shows the radial cross-section through a seal assembly in theform of a labyrinth seal,

FIG. 3 shows a water drop lying on a hydrophobic substrate,

FIG. 4 shows the detail “Z” of FIG. 1 and

FIG. 5 shows the radial cross-section through another seal assembly.

In FIG. 1, a seal assembly 1 can be seen that seals a first portion (airside) 2 of a machine part 3 in the form of a shaft from a second portion(oil side) 4. For this, the seal assembly 1 includes a seal element 5that has two seal lips 8 and 9—formed as a radial shaft seal—, whichabut on the shaft 3 in a rubbing manner.

The same applies to the embodiment according to FIG. 2 in which the sealassembly 1 is embodied as a labyrinth seal, whereby a gap 6 remainsbetween a seal element 5 and the shaft 3, which gap 6 should prevent thepenetration of moisture and/or dirt.

In order to improve the protection against the penetration of moisture,in particular water, and also dirt, the invention provides, in bothexemplary embodiments, that the seal element 5 as well as the machinepart 3 is provided or coated with a material 7 in the area of the sealelement 5, which material has super hydrophobic properties. That is, thematerial is applied to the seal element 5 and/or to the shaft 3 in arotationally symmetric manner.

The super hydrophobic material has the effect that moisture, and inparticular water, is repelled such that water drops form, as is shownaccording to FIG. 4 for the detail Z of FIG. 1. Here, the ingress ofwater into the seal assembly 1 can be expected from the left side. Awater drop 10 can be recognized here that forms in front of the seal gapdue to the super hydrophobic coating 7 and can not pass the seal lip 8.That is, if water contacts the coated surface at such a point, the superhydrophobic effect of the material 7 generates a water drop, or forlarger amounts of water a ring-shaped structure, as a consequence of thesurface tension of the water. Due to the V-shaped design of the gap, inwhose area the drop 10 is located, the water experiences a directionalpumping action here away from the seal lip 8. The markedly-higherhydrophobicity thus prevents the ingress of water into the seal gap andthus it can not be transported into the to-be-sealed space due to thenatural conveying capability of the seal edge. The above-mentionedring-shaped-structured water can also assist the sealing effect, inparticular vis-à-vis dust particles.

An ingress of water into the actual sealed region is prevented byupstream protective elements, such as radially- or axially-disposed seallips. Even small gaps, which can result from dynamic running deviations,are not surmounted due to the surface tension of the water.

Impregnation of non-woven materials in the protective seal also improvesthe protection against water and ensures a sufficient ventilation of themain seal element.

For the hydrophobicity of the proposed material 7 proposed according tothe invention, the following can be noted: The measure for the degree ofthe water-repellency (hydrophobe) of materials is the hydrophobicity.Substances that do not mix with water are designated with this and can,in most cases, bead water on surfaces. Non-polar materials, such asgreases, waxes, alcohols with long alkyl-residues (i.e. with theexception of methanol, ethanol and propanol), alkanes, alkenes, etc.,are hydrophobic. When dissolving some hydrophobic materials, such asmethane, in water, disadvantageous clathrate-structures entropicallyform. Therefore, the solubility of these materials in water is low.

The so-called contact angle θ is often utilized to identify the degreeof hydrophobicity. The angle is denoted as the contact angle, which aliquid drop (see water drop 10 in FIG. 3) on the surface of a solidforms relative to the surface of the solid. The size of the contactangle θ between the liquid and the solid depends on the interactionbetween the materials at the contact surface. The smaller thisinteraction is, the larger the contact angle is. In FIG. 3, the contactangle θ of a drop 10 lying there is depicted. Thus, in the determinationof the contact angle θ, a drop of the to-be-observed liquid contacts asolid substrate and is surrounded by gas. The contact angle is the anglethat is formed by the liquid at the point, at which the solid, liquidand gaseous phases meet.

Certain properties of the surface of a solid—such as for example thesurface energy—can be determined from the determination of the contactangle.

In the special case of the use of water as the liquid, the surface isdesignated as hydrophilic for small contact angles (θ is very small), ashydrophobic for angles around 90° and as super hydrophobic for evenlarger angles (like in FIG. 3). For very large angles (about 160°), thelatter is also designated as the Lotus Effect and corresponds to anextremely low wettability. The contact angle can be changed by surfacetreatment.

Generally speaking, hydrophobic surfaces are comprised of hydrophobicsubstances or are covered by hydrophobic substances. Examples are thecoating of surfaces with PTFE (Teflon) or the impregnation of insulatingmaterials and textiles with hydrophobic materials, such as wax orparaffin.

An extreme example for a hydrophobic surface is the surface of leavesand flowers of the lotus. This surface is rough and also covered withhydrophobic substances. Due to this distinctive attribute, this surfacehas a contact angle of over 160°, so that drops on it are almost round.Water beads up very well on such surfaces. Dirt particles lying thereonare rinsed away very easily. This effect is called the Lotus Effect.

In FIG. 5, another example of a seal assembly 1 is illustrated, in whichthe inventive design can be provided. The seal element 4 is embodiedhere as an elastomer part that forms three seal lips 11, 12, 13 intotal, which contact a contact ring 14. While the seal lips 11 and 12radially contact their counterface, the seal lip 13 axially contacts itscounterface. The seal lips, which thus act partially axially here, haveproven themselves, in particular in severely contaminated and wetenvironments, such as is found, e.g., in the case of a wheel bearing.

The invention preferably utilizes nano-filaments to generate the superhydrophobic effect in the material 7. For this, the following can benoted:

To generate a super hydrophobic effect, silicone nano-filaments arepreferably utilized according to the invention. These have a diameter ofabout 5 nm and a length of a few micrometers. They are produced fromsilanes. Chemically, they are constructed like silicone; however, due totheir nanostructure, they possess completely different physical andchemical properties.

The chemical structure of silicone nano-filaments corresponds to that ofsilicone. Silicon atoms are connected with each other via oxygen atoms.If more than two oxygen atoms serve as the bridge atoms,three-dimensional networks form. The fourth connecting point of thesilicon atom is then saturated by an organic residue.

Under certain conditions, no solid silicon-solid-body results on thesurfaces during the synthesis, but rather small filaments that are onlya few nanometers thick and only a few tens of nanometers long.

In one method, silicon nano-filaments can be produced from the gasphase. For this, trichlorosilane was vaporized in a reaction chambertogether with a precisely-set humidity and a substrate is exposed tothis mixture for several hours. In this case, it should be noted thatthe concentration of trichlorosilane and humidity is very precisely set;otherwise a condensation reaction takes place, i.e. it forms thesilicone, but no nano-filaments.

Silicone nano-filaments have a variety of, in some cases extreme,properties that can change into the extreme opposite by subsequentchemical modifications. Surfaces thus coated with siliconenano-filaments are extremely water-repellent (super hydrophobic), whichis utilized in the present case. Therefore, water drops lie as nearlyround balls on the surface; wetting scarcely occurs. This property isdescribed—as was explained—by the contact angle, which is nearly up to170° in the case of silicone nano-filament coatings. If the surface alsorises at even a small angle, e.g., a 2° slope, the beads immediatelyroll off from the surface.

The proposed design can be utilized on any seal assemblies. Thisapplies, for example, to sealing disks (simple metal covering disks)that are utilized in the axial end portion of a roller- or slidebearing, rotate with one of the bearing rings and frictionally abut onthe other bearing ring, thereby maintaining a gap with this bearingring, i.e. sealing in a friction-free manner. The invention can beutilized with all radial shaft seals that operate with conventional seallips or those made of PTFE. The idea can also be used in the same mannerin protective elements in the form of non-woven materials. This appliesin the same manner when radial shaft seal rings are utilized withaxially-acting protective lips that utilize separate contact rings.

REFERENCE NUMBER LIST

-   1 Seal assembly-   2 First portion-   3 Machine part (shaft, contact disk)-   4 Second portion-   5 Seal element-   6 Gap-   7 Material with super hydrophobic properties-   8 Seal lip-   9 Seal lip-   10 Drop-   11 Seal lip-   12 Seal lip-   13 Seal lip-   14 Contact ring-   Θ Water contact angle

1.-12. (canceled)
 13. A seal assembly comprising: a rotatable shaft anda radial shaft seal comprising at least one seal lip configured toslidably contact one of the shaft and a component connected with theshaft so as to seal a first portion of the shaft relative to a secondportion of the shaft, wherein a material having super hydrophobicproperties is disposed on at least a portion of an outer surface of atleast one of the shaft and the component connected with the shaft, thematerial being disposed adjacent to the seal element, and said materialis also disposed on at least a portion of an outer surface of the atleast one seal lip.
 14. The seal assembly according to claim 13, whereinthe outer surfaces having the super hydrophobic material disposedthereon exhibit a water contact angle (θ) of at least 150°.
 15. The sealassembly according to claim 14, wherein the super hydrophobic materialcomprises nano-filaments.
 16. The seal assembly according to claim 15,wherein the super hydrophobic material comprises siliconenano-filaments.
 17. The seal assembly according to claim 16, wherein thesuper hydrophobic material comprises polymethylsilsesquioxanenano-filaments.
 18. The seal assembly according to claim 17, wherein theat least one seal lip radially contacts the shaft or the componentconnected with the shaft.
 19. The seal assembly according to claim 17,wherein the at least one seal lip axially contacts the componentconnected with the shaft.
 20. The seal assembly according to claim 17,wherein the component connected with the shaft is one of a contact diskand a contact ring.
 21. The seal assembly according to claim 17, whereinthe outer surfaces are coated with the super hydrophobic material andexhibit a water contact angle (θ) of at least 170°.
 22. A seal assemblycomprising: a machine part and a labyrinth seal configured to seal afirst portion of a machine part relative to a second portion of themachine part, the labyrinth seal including at least one portionextending adjacent to the machine part so as to define a gap between thelabyrinth seal and the machine part, wherein a material having superhydrophobic properties is disposed on at least one surface that at leastpartially defines the gap or is adjacent to the gap.
 23. The sealassembly according to claim 22, wherein the machine part is coated withsaid material at least adjacent to the labyrinth seal.
 24. The sealassembly according to claim 22, wherein the at least one surface havingthe super hydrophobic material disposed thereon exhibits a water contactangle (θ) of at least 150°.
 25. The seal assembly according to claim 24,wherein the super hydrophobic material comprises nano-filaments.
 26. Theseal assembly according to claim 25, wherein the super hydrophobicmaterial comprises silicone nano-filaments.
 27. The seal assemblyaccording to claim 26, wherein the super hydrophobic material comprisespolymethylsilsesquioxane nano-filaments.
 28. The seal assembly accordingto claim 27, wherein the at least one surface is coated with the superhydrophobic material and exhibits a water contact angle (θ) of at least170°.
 29. An apparatus comprising: a machine part and a seal configuredto seal a first portion of the machine part relative to a second portionof the machine part, wherein a material having super hydrophobicproperties is disposed on the seal and on a surface adjacent to theseal.
 30. The apparatus according to claim 29, wherein the superhydrophobic material comprises silicone nano-filaments and each surfacehaving the silicon nano-filaments disposed thereon exhibits a watercontact angle (θ) of at least 160°.
 31. The apparatus according to claim30, wherein the super hydrophobic material comprisespolymethylsilsesquioxane nano-filaments.
 32. The apparatus according toclaim 31, wherein the water contact angle (θ) is at least 170°.